Old English sinder "dross of iron, slag," from Proto-Germanic *sendra- "slag" (source also of Old Saxon sinder "slag, dross," Old Norse sindr, Middle Low German and Middle Dutch sinder, Dutch sintel, Old High German sintar, German Sinter), from PIE root *sendhro- "coagulating fluid" (source also of Old Church Slavonic sedra "cinder").

Initial s- changed to c- under influence of unrelated French cendre "ashes," from Latin cinerem (nominative cinis) "ashes," from or related to Greek konis "dust" (see incinerate). The Latin word was contracted to *cin'rem and the -d- inserted for ease of pronunciation (compare peindre from pingere). The French word also apparently shifted the sense of the English one to "small piece of burnt coal" (16c.). Volcanic cinder cone is recorded from 1849.